From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-23.2 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_IN_DEF_DKIM_WL autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 82E60C433B4 for ; Mon, 5 Apr 2021 23:46:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3C60B61005 for ; Mon, 5 Apr 2021 23:46:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242068AbhDEXqa (ORCPT ); Mon, 5 Apr 2021 19:46:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48758 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237853AbhDEXq2 (ORCPT ); Mon, 5 Apr 2021 19:46:28 -0400 Received: from mail-ot1-x32f.google.com (mail-ot1-x32f.google.com [IPv6:2607:f8b0:4864:20::32f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B2661C06174A for ; Mon, 5 Apr 2021 16:46:21 -0700 (PDT) Received: by mail-ot1-x32f.google.com with SMTP id s16-20020a0568301490b02901b83efc84a0so4021360otq.10 for ; Mon, 05 Apr 2021 16:46:21 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=CTdV629ZhMgRAehKkgmyuxBMkQiqLv+0INgoX/85OgY=; b=QUzjliudZ5IBbeJ4LJDfU1XRaXig20/Dtad2yxZBNPAegCSx4hA8C2ovxzv2QgmQAA 4NIJu59Nyowyw8Gf6V7PBg626xMLNLCB5qxeo/FDJRfqD5tuYOK47LQBFe5PIwCOYukK Tdvsrefr1sAjW45TI+/rSAPRPmwhyBqOJSqpJ8zXhWF2+tNNJ3fCugZN/WP30EaBjiJ4 kQuhWNQS+Y8vxkbERbIdAkaz5f1cALD8CbVWBeN1RPJUZpuUFgFurN1BQDT6UUonL/yR 7F9fsFcyoP1jdWBdpScVykiNRzYkQ/qh+neN7AGvrgHm03b2H7H07Luq5bEDzowDswWz rIig== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=CTdV629ZhMgRAehKkgmyuxBMkQiqLv+0INgoX/85OgY=; b=itGt/ge9mL3rGBXhp8KZEJ4Xh0ZtjAEwg3IidxnuC3ljzyoN+JlwPH5/hHim3lhE9L EXtJo93UvMm9UCT5RE8bBOuEOvfFyao9VyCG5p3ZN7+cD/XZ2+p9x3fprXc/wDvrQIqW w6m2DztdwBudFRBNQ2kjBtjM6mh06Mhzp7DJaHN0pMfkvE0TlP25VI02pkRZcNfiVbTC Y7ABMN7wgiO9FzS4HT1A5HlEacVCuyiil15pJmuJZPz6Z3DVw6YUivwqh8SLydDKP7nR ejHP9T3BRsTOkCf4Mf32494BL+qe3YlcqPER6UJy6HSJLa5p4yIf92u5kLlSqon64fSI Sw3w== X-Gm-Message-State: AOAM531CDOJml1qbiXZW3f6i90kzOaVo4136RxZqkspmCcTI49oDXK3y 8vcpiRWq234Jk2/Z9jsvGSHw4Q00sSuyNMikhTisxA== X-Google-Smtp-Source: ABdhPJwCM1A2Jh9U35cxNbSDkipZ/Qb09Xy2Nr3JFPIBM/f6nAunfi1K81wAVxPZlUAkcJKtlWSNkxJu8mndUTxWhDg= X-Received: by 2002:a9d:5508:: with SMTP id l8mr24572016oth.233.1617666380817; Mon, 05 Apr 2021 16:46:20 -0700 (PDT) MIME-Version: 1.0 References: <20210405220647.1965262-1-pcc@google.com> In-Reply-To: From: Marco Elver Date: Tue, 6 Apr 2021 01:46:09 +0200 Message-ID: Subject: Re: [PATCH v2] kasan: fix kasan_byte_accessible() to be consistent with actual checks To: Andrey Konovalov , Andrew Morton Cc: Peter Collingbourne , Dmitry Vyukov , Alexander Potapenko , Evgenii Stepanov , Linux Memory Management List , LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 6 Apr 2021 at 00:43, Andrey Konovalov wrote: > On Tue, Apr 6, 2021 at 12:07 AM Peter Collingbourne wrote: > > > > We can sometimes end up with kasan_byte_accessible() being called > > on non-slab memory. For example ksize() and krealloc() may end up > > calling it on KFENCE allocated memory. In this case the memory will > > be tagged with KASAN_SHADOW_INIT, which a subsequent patch ("kasan: > > initialize shadow to TAG_INVALID for SW_TAGS") will set to the same > > value as KASAN_TAG_INVALID, causing kasan_byte_accessible() to fail > > when called on non-slab memory. > > > > This highlighted the fact that the check in kasan_byte_accessible() > > was inconsistent with checks as implemented for loads and stores > > (kasan_check_range() in SW tags mode and hardware-implemented > > checks in HW tags mode). kasan_check_range() does not have a > > check for KASAN_TAG_INVALID, and instead has a comparison against > > KASAN_SHADOW_START. In HW tags mode, we do not have either, but we > > do set TCR_EL1.TCMA which corresponds with the comparison against > > KASAN_TAG_KERNEL. > > > > Therefore, update kasan_byte_accessible() for both SW and HW tags > > modes to correspond with the respective checks on loads and stores. > > > > Link: https://linux-review.googlesource.com/id/Ic6d40803c57dcc6331bd97fbb9a60b0d38a65a36 > > Signed-off-by: Peter Collingbourne > > --- > > mm/kasan/kasan.h | 3 +-- > > mm/kasan/sw_tags.c | 10 +++++++--- > > 2 files changed, 8 insertions(+), 5 deletions(-) > > > > diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h > > index 8c55634d6edd..e18e8da35255 100644 > > --- a/mm/kasan/kasan.h > > +++ b/mm/kasan/kasan.h > > @@ -368,8 +368,7 @@ static inline bool kasan_byte_accessible(const void *addr) > > u8 ptr_tag = get_tag(addr); > > u8 mem_tag = hw_get_mem_tag((void *)addr); > > > > - return (mem_tag != KASAN_TAG_INVALID) && > > - (ptr_tag == KASAN_TAG_KERNEL || ptr_tag == mem_tag); > > + return ptr_tag == KASAN_TAG_KERNEL || ptr_tag == mem_tag; > > } > > > > #else /* CONFIG_KASAN_HW_TAGS */ > > diff --git a/mm/kasan/sw_tags.c b/mm/kasan/sw_tags.c > > index 94c2d33be333..00ae8913fc74 100644 > > --- a/mm/kasan/sw_tags.c > > +++ b/mm/kasan/sw_tags.c > > @@ -121,10 +121,14 @@ bool kasan_check_range(unsigned long addr, size_t size, bool write, > > bool kasan_byte_accessible(const void *addr) > > { > > u8 tag = get_tag(addr); > > - u8 shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(kasan_reset_tag(addr))); > > + void *untagged_addr = kasan_reset_tag(addr); > > + u8 shadow_byte; > > > > - return (shadow_byte != KASAN_TAG_INVALID) && > > - (tag == KASAN_TAG_KERNEL || tag == shadow_byte); > > + if (untagged_addr < kasan_shadow_to_mem((void *)KASAN_SHADOW_START)) > > + return false; > > + > > + shadow_byte = READ_ONCE(*(u8 *)kasan_mem_to_shadow(untagged_addr)); > > + return tag == KASAN_TAG_KERNEL || tag == shadow_byte; > > } > > > > #define DEFINE_HWASAN_LOAD_STORE(size) \ > > -- > > 2.31.0.208.g409f899ff0-goog > > > > Reviewed-by: Andrey Konovalov > > Thank you, Peter! Reviewed-by: Marco Elver Thanks!